Are you really cheap like me? Can't afford $9 for a water bottle holder? Then make this, out of a coathanger.
You will need.
(1) coathanger
some various screws and washers
2 pliers (I used pliers and channel locks, just what I had near my desk.
Electrical tape
Drill and drillbit
Ok, you will need about 20 minutes to make it, and 10 to install it.

Step 1: Get Your Stuff and Start Bending

First, I find it easier if you take your coathanger and make it straight, that way there are no confusing bends to wrap your mind around.

Then find a style of holder you like on the internet, I chose this one. (see photo

Step 2: Done Bending?

Here's what mine looked like after bending it to shape.
Test it first, bottle should fit. I also tested mine with a clean canteen (metal water bottle) that's a bit different shape. Took a while to get a shape that worked for both. Use your tape to tape the ends together

Step 3: Mounting

Ok, now grab your drill, screws, and washers. Take your washers and kinda bend them a bit so it fits the curve of your tube for a tighter fit. I used wood screws, but really anything that fits tightly will work. Mark and drill your holes, put your washers on. And test it out. If it falls out while riding (like mine did) Just bend it tighter. That's the beauty of this design, it's super easy to adjust.

Step 4: Final Shot/closing Remarks

Ok you made it, now go hit the trails. Or post pictures of different designs you have tried. Cool designs go in this final section. (yep, your picture, in this instructable)